Also for those interested, there's an open source project which will do this too, given GTFS data: http://docs.opentripplanner.org/en/latest/Intermediate-Tutori

Also for those interested, there's an open source project which will do this too, given GTFS data: http://docs.opentripplanner.org/en/latest/Intermediate-Tutorial/#calculating-travel-time-isochrones http://docs.opentripplanner.org/en/latest/Intermediate-Tutor... It's extremely fiddly to set up but it's also a lot more detailed.